This invention relates to the field of tools for automobile mechanics, and particularly to a tool for extracting hydraulic valve lifters in engine overhaul.
Many modern internal combustion engines have hydraulic valve lifters located between the ends of exhaust and intake valve push rods and the cam actuated rocker arms provided to displace the valves against their springs. Removal of these lifters for inspection and replacement if necessary comprises one of the common tasks of a mechanic. The lifters are generally cylindrical and are generally retained in cylindrical openings for engaging the engine camshaft at their first ends. They are thus located well within the engine, frequently at the bottom of a push rod passage of considerable depth which traverses one or more transverse restrictions. When only a known one of these lifters requires replacement, it is advantageous to be able to do this while avoiding as far as possible the wholesale disassembly of the engine which accompanies a general overhaul. A tool which can be operated through long passages of limited cross section is thus desirable, and such tools are taught in Bowden U.S. Pat. No. 3,252,210 and Tutino U.S. Pat. No. 3,681,838, for example.
One factor requiring lifter replacement is the build-up of gum or varnish on the lifter. The same factor makes removal of the lifter difficult, and requires an extractor capable of applying considerable axial force to the lifter, even to the extent of providing an impact hammer arrangement, as is taught in Miller U.S. Pat. No. 2,943,385. When the space limitations set by the configuration of the end of the lifter which must be engaged by an extractor are considered, the problem of making an extractor small enough and yet strong enough becomes quite difficult.